Unidirectional infiltrated PI/SiO2 composite aerogels with a confined reinforcing strategy for integrated thermal and acoustic insulation

It is of great significance to develop integrated thermal insulation and noise reduction materials for energy saving and pollution control. As a nanoporous material, aerogels have excellent thermal and acoustic properties, however, the thermal stability of organic aerogels is insufficient, and the mechanical properties of inorganic aerogels limit their practical application. Herein, we designed a confined reinforcing strategy for organic-inorganic composite aerogels with high strength and excellent acoustic insulation properties. A directional freezing technology was utilized to control the pore structure of a polyimide (PI) aerogel, and then a continuous SiO2 aerogel was filled in the unidirectional pore channels, forming a double-network structure consisting of both PI and SiO2 aerogels. The results showed that the compressive strength of the composites was 1.83 MPa at 10% strain, the initial thermal decomposition temperature was about 530 °C, and the lowest thermal conductivity was 22.37 mW m−1·k−1 at radial direction. Moreover, the average sound transmission loss (STL) of the composites with an 18 mm thickness was 30–33 dB in the range of 500–6300 Hz. This confined reinforcing strategy can safeguard fragile aerogels while maximize their inherent characteristics, which offers a novel approach to the creation of multi-functional aerogel composites.